Core G: Nutrition and GI Core (Clinical Research Core) Staff of the core will include Core Director Sherwood Gorbach, M.D. He is professor of Medicine in the Department of Family and Community Health at Tufts School od Medicine and Physician in the Division of Community Health at New England Medical Center. Dr. Gorbach will provide oversight of the nutritional and GI testing services offered by the core, the nutritional survey training that will be offered through the core, coordinate additional community outreach activities of the CFAR, and serve on the Executive Committee of the CFAR. The core staff will include a nutritionist who will perform dietary intake surveys, perform anthropometric studies, and train investigators in survey usage; and a technician who will performed body composition and energy expenditure studies. The basic purpose of the core is to allow investigators to elucidate the impact of HIV infection on the nutritional status and gastrointestinal function of their clinical study subjects at all stages of the disease process. This purpose will be specialized testing of GI function as well as consultative services on GI function test performance and interpretation; testing services for body composition and energy metabolism function; and specialized services for testing and modeling of Cryptosporidium parvum infection. Key scientific studies to be supported by this core include the CDC-funded HIV Epidemiology Research Study (HERS; PI. Charles Carpenter, M.D.); Dr. Susan Cu-Uvin's study of the effect of highly-active anti-retroviral therapy on viral load in the female genital tract, which will form the basis of an assessment and intervention regarding nutritional status to be done as an extension of Dr. Sherwood Gorbach's Nutrition for Life program project. The core will also support the set of studies being conducted in the Tufts University School of Veterinary Medicine that are exploring the molecular basis of Cryptosporidium attachment and infection, immune response to infection, and possible molecular targets to effective immunotherapy.